Georgeta Burtica

The electrochemical determination of phenolic derivates using multiple pulsed amperometry with graphite based electrodes.

The electrochemical determinations of 4-chlorophenol (4-CP) and 4-nitrophenol (4-NP) by chronoamperometry (CA) and multiple pulsed amperometry (MPA) using expanded graphite-epoxy composite (EG-Epoxy) and rotating spectral graphite disc (SG) electrodes are reported. The electrochemical behaviours of both electrodes in the presence of organics informed about oxidation peak potential and the electrode fouling with organics concentration increasing. Setting up the oxidation peak potential as detection potential, only SG gave good electroanalytical performance using CA. However, by MPA applying both electrodes exhibited the capability to assess electrochemically and quantitatively the pollutants from aqueous solutions. UV spectrometric method detecting 4-CP and 4-NP at lambda=280nm and lambda=398nm wavelength, respectively was used for validation and parallel determinations.

Voltammetric Detection of Urea on an Ag-Modified Zeolite- Expanded Graphite-Epoxy Composite Electrode

In this paper, a modified expanded graphite composite electrode based on natural zeolitic volcanic tuff modified with silver (EG-Ag-Z-Epoxy) was developed. Cyclic voltammetry measurements revealed a reasonably fast electron transfer and a good stability of the electrode in 0.1 M NaOH supporting electrolyte. This modified electrode exhibited moderate electrocatalytic effect towards urea oxidation, allowing its determination in aqueous solution. The linear dependence of the current versus urea concentration was reached using square-wave voltammetry in the concentrations range of urea between 0.2 to 1.4 mM, with a relatively low limit of detection of 0.05 mM. A moderate enhancement of electroanalytical sensitivity for the determination of urea at EG-Ag-Z-Epoxy electrode was reached by applying a chemical preconcentration step prior to voltammetric/amperometric quantification.

Carbon-based Composite Electrodes : Preparation, Characterization and Application in Electroanalysis

Electrodes based on carbon, i.e., expanded graphite (20%, wt.)-epoxy composite (20EG-Epoxy) and expanded graphite (20%, wt.)-polystyrene composite (20EG-PS) have been prepared, characterized using scanning electron microscopy (SEM) and cyclic voltammetry (CV), and tested as anodic sensors. The electrodes exhibited good mechanical resistance and low electrical resistances. Scan rate dependent cyclic voltammetry responses at 20EG-Epoxy and 20EG-PS composite electrodes, which were exemplified for thiourea (TU), a toxic sulphur organic compound selected as testing target analyte in 0.1 M Na2SO4 supporting electrolyte, were investigated. The obtained voltammetric data were in accordance with those for a random array of microelectrodes. The voltammetric and chronoamperometric detection results of TU in tap water samples, without a supplementary addition of supporting electrolyte, at 20EG-Epoxy electrode proved its use for direct analysis of environmental samples.

Photocatalytically-assisted electrochemical degradation of p-aminophenol in aqueous solutions using zeolite-supported TiO2 catalyst

This paper reports the results of an investigation into enhancement of the electrochemical oxidation of p-aminophenol (4-AP) in an aqueous solution with a boron-doped diamond (BDD) electrode, assisted by photocatalysis using a zeolite-supported TiO2 (Z-TiO2) catalyst. The BDD electrode was characterised in 0.1 M Na2SO4-supporting electrolyte and the presence of 4-AP by open-circuit potential behaviour (OCP) and cyclic voltammetry (CV). The electrode behaviour was investigated in the dark and following UV irradiation and in the absence/presence of the Z-TiO2 catalyst. The electro-oxidation process was carried out using chronoamperometry (CA) and multiple-pulsed amperometry (MPA) at the selected potential under potentiostatic conditions. The electrochemical degradation process of 4-AP on the BDD electrode was improved by the application of a pulsed potential, which allowed both in-situ electrochemical cleaning of the electrode and indirect oxidation of 4-AP by oxygen evolution. The application of photocatalysis using Z-TiO2 in the 4-AP electrochemical degradation exhibited an enhanced effect when the anodic potential was set at +1.25 V vs. Ag/AgCl in the water stability region, close to the oxygen evolution potential.

Carbon Composite Electrodes Applied for Electrochemical Sensors

Electrodes based on particulate carbon-epoxy or polystyrene composites, have been formed and characterized using electrochemical methods. The working electrodes made of various forms of graphite or carbon and using different polymers, a type of expanded and exfoliated graphite-epoxy (EEG-Epoxy), carbon nanofiber-expanded graphite-epoxy (CNF-EG-Epoxy), expanded graphite-polystyrene (EG-PS), expanded graphite-epoxy (EG-Epoxy) were tested for electrochemical sensing of various organic pollutants in aqueous solution. The prepared carbon composite electrodes showed good mechanical strength, low electrical resistance, and easy new surface by simple polishing, all useful characteristics for electroanalytical purposes. The electrochemical performance of these electrodes was studied by cyclic voltammetry (CV), linear-scan voltammetry (LSV), chronoamperometry (CA), differential pulsed voltammetry (DPV), and square-wave voltammetry (SWV).

SPECTROPHOTOMETRIC PARAMETERS FOR ORGANIC MATTER CHARACTERIZATION IN RAW AND TREATED SURFACE WATER

This study aimed to assess the coagulation performance using simple aluminum sulfate (Alum) and pre-hydrolyzed polyaluminum chloride (PACl) coagulation agents by conventional global parameters, i.e., turbidity and organic matter expressed by total organic carbon (TOC) and chemical oxygen demand (COD), and non-conventional spectrophotometric parameters. Non-conventional spectrophotometric parameters, expressed as absorbance recorded at different wavelengths, i.e., A254, A280, A365, allowed distinguishing some components classes with different degrees of activation, which are parts of natural organic matter (NOM) from drinking water. Monitoring the A254/A280 ratio in coagulation stage allowed determining the removal efficiency of some undesirable humic compounds with increased activity, which exhibited the trihalomethanes (THMs) formation potential during disinfection stage. Monitoring the A254/A365 ratio in coagulation stage allowed determining the removal efficiency of some undesirable humic compounds with hydrophobic character. All experimental results showed that the specific absorbance (SUVA) parameter expressed as the ratio between A254 and dissolved organic carbon (DOC), can be used successfully to characterize NOM from raw water and predicts DOC removal in coagulation step. The correlation between conventional and non-conventional parameters showed a better performance of coagulation performance using PACl in comparison with Alum coagulation agent.

SUSTAINABLE DEVELOPMENT AND ENVIRONMENTAL EDUCATION

The higher education and the scientific research are subjected to the action of three major factors: globalisation, technology and competition and their answer has to be: flexibility, efficiency and assessment on the development of the intellectual creativity. On the basis of these concepts, this paper presented briefly the management of the teaching and research activities at the Environmental Department of the Faculty of Industrial Chemistry and Environmental Engineering Timisoara. It was carried out the teaching activity accommodation to sustainable development, materialized by the involving of the teachers and the students, in the spirit of “team-working” on the research with applicative character (e.g. the good collaboration with “Aquatim” Company). The aim of the projects is to build the practical environmental skills of the students in the following environmental fields: drinking water and wastewater treatment.